How on earth would SF's mother know when KK arrived? She may have been busy caring for baby K or may not have been at home. Good luck to the DA in proving she knew.
Just because KK claimed SF came on to the porch during the fire doesn't mean it is true or that SF knew what was being burned. This case isn't some kind of formula fiction where we get to decide the ending. LOL
JMO
SF's word on the fire is important as confirmation of KK's story. Yes, KK took them to a spot where there had been a fire, but right now we only have her word that the fire took place when she said it did. PF and SF are the only two people who can confirm that there actually was a fire on that evening. Only PF can confirm what was burned, although SF could give hints based perhaps on the smells or smoke.
SF is one of only a couple people who can potentially testify as to when PF arrived at the ranchette on Thanksgiving Day with Baby K.
Something that I wondered about: LE found bits of black plastic and traces of an accelerant where the fire took place. According to KK, PF set the fire inside a round tank. PF was going to 'scoop' up the remains and dispose of them elsewhere.
If the tote and firewood were in the tank when the fire was built, presumably PF 'scooped' up the whole tank. So how did black plastic and traces of accelerant get left behind?
One fake scenario: PF could claim that anything the investigators found was from an old fire that was from before KB 'disappeared'. Right now, we don't have any evidence to the contrary - not that we are aware of, anyway.
SF's testimony could also back up or refute KK's story that she ate pizza, took an ibuprofen for her headache, and took a rest. I guess she could claim that she went straight to bed after Thanksgiving Dinner and didn't wake until morning, so she had no idea there was a fire or that KK was ever there.
If I were SF, I'd be careful about playing the 'memory' card. If she paints herself as a forgetful old lady who has trouble physically getting around, she's not exactly painting a good picture for someone who has hopes of getting custody of a healthy little grandchild. Not a good fit to put a little girl in the hands of an old lady with memory issues and physical limitations. living alone on a somewhat isolated property.